High volumetric energy density annealed-MXene-nickel oxide/MXene asymmetric supercapacitor

Abstract

A Ti₃C₂T_x MXene electrode decorated with NiO nanosheets was synthesized by a facile and cost-effective hydrothermal method. The NiO nanosheets were grown and immobilized on the carbon-supported TiO₂ layer which was derived from Ti₃C₂T_x-MXene during a thermal annealing process. An electrode based on the NiO-grown derived-TiO₂/C-Ti₃C₂T_x-MXene nanocomposite (Ni-dMXNC) exhibited a remarkable maximum specific capacity of 92.0 mA h cm⁻³ at 1 A g⁻¹ and 53.9 mA h cm⁻³ at 10 A g⁻¹. Furthermore, an asymmetric supercapacitor (ASC) device composed of Ni-dMXNC as the positive electrode and Ti₃C₂T_x MXene as the negative electrode was demonstrated to be better with a high energy density of 1.04 × 10⁻² W h cm⁻³ at a power density of 0.22 W cm⁻³, and cycling stability with 72.1% retention after 5000 cycles, compared to ASCs using previously reported Ti₃C₂T_x MXene materials. The enhanced capacitive performance is attributed to the newly formed high-surface-area multilayers of the Ni-dMXNC architecture, the active surface of NiO layer, and a favourable synergetic behaviour of the Ti₃C₂T_x MXene negative electrode.